Manufacture of artificial fibers



May 29, 1934.

A. KAMPF MANUFACTURE OF ARTIFICIAL FIBERS Filed Aug. 1, 1930 2 Sheets-Sheet l May 29, 1934. A, KAMPF 1,960,634

MANUFACTURE OF ARTIFICIAL FIBERS- Filed Aug. 1, 1930 0 Q d -15m I mr- 5m par-Z 5m I xv-10 0w 2 Sheets-Sheet 2 g Patented May 29, 1934 1,960,634 MANUFACTURE OF ARTIFICIAL FIBERS Adolf Kiimpf, Premnitz, Germany, assignor to Farbenindustrie Aktiengesellschaft,

Frankfort-on-the-Main, Germany Application August 1, 1930, Serial No. 472,412 In Germany August 14, 1929 3 Claims. (01. 18-54) My present invention relates to the manufacture of artificial silk and more particularly to a specific stretching operation to which the threads are subjected on their way from the spinning nozzle to the collecting device.

The endeavours made from the very beginning of artificial silk industry which aim to improve the textile properties of the fiber by stretching the silk fibers and silk threads during the spinning process, are known. For this purpose, there has for a long time past especially been made use of successive rollers, drums or bobbins having diiferent peripheral velocities which increase in the direction of the travel of the thread, so that between the two revolving bodies the fibers are stretched in a degree corresponding with the ratio between the peripheral velocities.

Hitherto the second of two such rollers has at the same time been used as a collecting device for 20 thethreads. With this arrangement it cannot be avoided that the thread is very tightly wound on the second roller or collecting device. Considering this roller or collecting device alone it is clear that the degree of stretching that is the draught to which the individual fiber is subjected from its very issue from the nozzle, depends on the ratio of the discharge velocity of the spinning mass from the nozzle to the speed with which the thread is wound on the collecting device. .By

guiding the freshly coagulatedthreads over a plurality of successive drums or rollers rotated with correspondingly increased peripheral velocities, it becomes possible to separate the total draught into several phases.

3 This way of performing the stretching operation will become quite clear by reference to the adhering drawings in which Fig. 1 is a front view in which the threads are collected on a bobbin.

The first phase of draught occurs between the spinning nozzle and the first roller 4, and the second phase between the two rollers 4 and 5. If, for instance, the discharge velocity from the nozzle amounts to 20 meters and the peripheral speed of the roller 4 to 25 meters, the partial draught in the first phase will be 1.25; if, furthermore, the peripheral speed of the roller 5 is, for instance, 40 meters, the partial draught between the rollers 4 and 5 is 1.6 and the total draught between the spinning nozzle and the roller 5 amounts to 2.

The present invention is based on the important observation that in the wet spinning of cellulose solutions the best fibers are generally obtained by keeping the partial draught of the first phase as tion is intended to indicate a correspondent operation as performed in spinning natural fibers. In the present case it indicates the quotient:

winding speed of the threads on the collecting device discharge velocity of the spinning mass measured in the spinning opening,

while the term partial draught indicates a correspondent quotient of the velocity with which the thread is guided away by one part of the machine and of the velocity with which it is delivered from the foregoing part.

These details may become more clearly by the adhering sketch (Fig. 3) showing diagrammatically difierent phases of draught executed on the thread between the spinning nozzle and the collecting device. For the sake of clarity, the precipitating bath and the collecting device are not shown and the distances of the draught rollers over which the thread is once guided, the figures 76 indicating their peripheral velocity of the spinning liquid and the discharge velocity measured in the spinning opening, are chosen voluntary. According to my invention, the discharge velocity of the spinning mass from the nozzle should be 30 greater than the speed'with which the coagulating fibers are drawn from the bath by the first spool 4. It remains to say that under these con-- ditions owing to the shrinking of the freshly precipitated threads no spinning liquid or regenerated cellulose is accumulated in the precipitating bath. Having in mind that the jet 'of spinning liquid is liable to a shrinkage up to about 66 per cent by the-entrance into the coagulating bath and that this shrinkage not only occurs with respect to the thickness but, likewise, in the direction of the longitudinal axis of the thread formed, it is evidenced that the draught between the spinning nozzle and the first reception device may be diminished without difiiculties, so as to be lower than 1. That is to say the peripheral velocity of the draught roller which draws 011 the threads coming from the spinning nozzle may be lower-than the speed of the spinning mass discharged from the said nozzle.

According to my invention, it is even possible to draw the thread from the bath at a speed being, for instance, only one third of the speed at which the spinning liquid is ejected from the nozzle. Just with a particularly low partial draught in the first phase, a strong draught may be effected in the second phase, whereby the fiber produced is not at all detrimentally affected, but is even strengthened in an astonishingly favorable manner.

It is not advisable to increase the. partial draught between the spinning nozzle and the first roller 4 beyond the limit indicated lower than 1. Before effecting the final draughtfithe mi-cellar' composition must have been brought to a certain density, so as to obtain and retain in the finished fiber the radiographically demonstrable oriented structure of the crystallites which is characteristic of a high tenacity.

Therefore, according to the process described, the decisive draught for the final product is produced by the second roller 5, whereat the thread is stretched in a correspondent strong manner. In View of this stretching, it is not desirable to collect the thread on the roller 5 itself, but the roller 5 is only used as draught roller and another third spool or roller 7 is inserted as a collecting device having approximately the same or, if necessary, a somewhat increased peripheral velocity as compared with the second roller 5. The thread is thus collected by the receiving device 7 while being only moderately stretched. This receiving device may also be constructed so as to serve as a delivery roller for a centrifuge which is mounted behind it.

The surprising effect of the present invention,

therefore, resides in the certainty with which an artificial fiber of high tenacity can be produced. The conditions of draught, in this case, are such that the thread is drawn off from the nozzle with a speed which is smaller than that with which it leaves the nozzle. This result may even be obtained when the thread is collected by the receiving device with a speed inferior tothat with which the spinning liquid is ejected from the nozzle, so that both'the partial draught in the first phase between the nozzle and the first draught roller 4' and the total draught are less than 1.

ti The following example illustrates the inven- Unripened viscose without degrees of ripeness according to Hottenroth containing 5 per cent of cellulose, and made from alkali cellulose which has not been ripened or ripened only to a small extent, is spun at ordinary temperature through nozzles having apertures of 0.08 mm. in a spinning bath containing besides 38 per cent of sulfuric acid somuch carbozoltetrasulfonic acid that the total acid content amounts to 47 per cent,

- calculated as monohydrated sulfuric acid. The

bath may contain, for instance, 5 per cent of sodium sulfate which cannot be avoided in spinning. The passage through the bath may be 25 cm., the passage through the air to the first draught roller 20 cm., the partial draught between the nozzle and the first draught roller 0.4, the partial draught between the first and the second draught roller2 and consequently the total draught 0.8. Furthermore, the distance of air between the two draught rollers may be 30 cm.

and the distance between the draught roller 5 and the collecting spool 7, cm. In passing over the draught roller and the delivery roller the thread is guided by means of the arms 6a, 6b and 6c of a suitably fixed thread guide 6, so that it is not iniured by any friction which may occur betweenthe thread delivered to and that leaving the roller.

This mode of operating permits of producing with great regularity artificial silk threads of finest individual titen having a tenacity of 3.5 g. and more pro denier.

According to the kind of the cellulose solutions, the precipitating bath and other spinning conditions, it may be advantageous to, continuously treat the thread on one of the draught rollers or on the receiving device with a washing liquid either by immersing the spool in a suitable bath or by irrigating it by said washing liquid. This feature has only been mentioned for completeness sake as it is not an object of this invention. 4

My invention is not limited to tne example given or to the specific details mentioned therein. It is obvious that other viscose solutions which may be ripened or which may contain another amount of cellulose make necessary another mode of operation with respect to the draught executed on the freshly coagulated threads. The same holds true with respect to the composition of the precipitating bath.

Furthermore, the inventive idea of my present specification may be employed when spinning threads from other cellulose solutions according to the wet spinning process as, for instance, according to the cupro-ammcniurn spinning process. Or I may divide the total draught into more phases by guiding the thread over a corresponding plurality of draught rollers. A few simple comparative experiments should be made to determine the best performance of my invention with a particular viscose or precipitating bath and I contemplate as included within my-invention all such modifications as fall within the scope of the appended claims.

What I claim is:

1. In the manufacture of fine artificial fibers according to the wet spinning process in which the freshly coagulated threads, on their way from the spinning nozzle to the collecting device, pass at least two stretching devices, the .step which comprises acting upon the thread between the spinning nozzle and the first draughting device with a draught of at least 0.25, but smaller than 1, said draught being indicated by'the quotient: peripheral velocity of the first draught roller discharge velocity of the spimiing mass.

2. In the manufacture of fine artificial fibers according to the wet spinning process in which the freshly coagulated threads, on their way from the spinning nozzle to the collecting device, pass at least two stretching devices, the step which comprises acting upon the thread between the spinning nozzle and the collecting device with a total draught of at least 0.25, but smaller than 1, said draught being indicated by the quotient: winding speed of the collecting device discharge velocity of the spinning mass.

3. In the manufacture of fine artificial fibers according to the wet spinning process in which the freshly coagulated threads, on their way from the spinning nozzle -to the collecting .device, pass at least two stretching devices, the step which comprises acting upon the thread between the spinning nozzle and the collecting device in some single phases with a total draught of at least 0.25, but smaller than 1, said draught being indicated by the quotient: winding speed of the collecting device discharge velocity of the spinning mass.

mom KAMPF. 

